How should Jerusalem remain exempt from God’s wrath if she is no different from Nineveh? In times past, when disaster struck the people would turn from their sins and call on Jehovah. Now they simply turn to ever worse sins. Political and religious leaders alike twist their roles completely backward. While they did thus, God had been the very definition of faithfulness, having lived in their midst the whole time. He manifested His justice to them daily; they openly shamed Him. He destroyed their enemies, demonstrating His power. Surely the would respect Him after all He did! No, she begged for the same treatment by sinning even worse than those who threatened her.
Israel refused to distinguish herself among nations as God’s own unique people. So when He gathers the entire world together for That Day, the nation will take her share of wrath. His judgment will wipe away sin, which of course means He will remove those who cling to it. This purging will see a remnant from all nations respond and turn to Him. People from all over the entire world would worship His Name. So it would be they would all stand with the righteous remnant of Judah. Whatever is left will not act anything like the kingdom He was going to crush in just a short time.
Of course, there can be no literal fulfillment of this. Rather, Zephaniah is seeing with spiritual eyes the day when the Messiah would come and bring forth a New Covenant to all mankind. The image drawn here symbolizes the Kingdom of Heaven, not a politically restored Judah. His wrath against sin reached a climax at the Cross.
So it’s only natural to expect joy unspeakable. The Lord calls on the ancient City to rejoice in the rise of the New Israel. His own Son, the true Messiah, would rule over the people in this Eternal Kingdom, in a Spiritual Jerusalem. Everything Israel was meant to be will return, unassailable against all sin. Those who refuse to join in this spiritual celebration would be excluded. The old shadowy political Israel would be forgotten. We see in Zephaniah’s final words echoes prefiguring the message of Christ, the Good Shepherd. He will restore His fame by His own hand, making His people the blessed nation others would scramble to join.